Interceptor拦截器

Interceptor介绍

SpringMVC 内置拦截器机制 ，允许在请求被目标方法处理的前后进行拦截，执行一些额外操作；比如：权限验证、日志记录、数据共享等

Spring Interceptor是一个非常类似于Servlet Filter 的概念 。

过滤器和拦截器的区别

	拦截器	过滤器
接口	HandlerInterceptor	Filter
定义	Spring 框架	Servlet 规范
放行	preHandle 返回 true 放行请求	chain.doFilter() 放行请求
整合性	可以直接整合Spring容器的所有组件	不受Spring容器管理，无法直接使用容器中组件 需要把它放在容器中，才可以继续使用
拦截范围	拦截 SpringMVC 能处理的请求	拦截Web应用所有请求
总结	SpringMVC的应用中，推荐使用拦截器

自定义 Interceptor

如果你需要自定义 Interceptor 的话必须实现 org.springframework.web.servlet.HandlerInterceptor接口并且需要重写下面下面3个方法：

public boolean preHandle(HttpServletRequest request,
                         HttpServletResponse response,
                         Object handler)
 
 
public void postHandle(HttpServletRequest request,
                       HttpServletResponse response,
                       Object handler,
                       ModelAndView modelAndView)
 
 
public void afterCompletion(HttpServletRequest request,
                            HttpServletResponse response,
                            Object handler,
                            Exception ex)

注意：

• preHandle方法返回 true或 false。如果返回 true，则意味着请求将继续到达 Controller目标方法 被处理。
• preHandle返回true，afterCompletion 方法才会执行，而且是倒序执行
• postHandle是controller目标方法执行之后，才执行

配置Interceptor

配置拦截器，需要实现WebMvcConfigurer并重写addInterceptors方法

@Component
public class WebConfig implements WebMvcConfigurer {
    @Override
    public void addInterceptors(InterceptorRegistry registry) {

       registry.addInterceptor(firstInterceptor).addPathPatterns("/api/*");

    }

案例

创建拦截器

• FirstInterceptor:拦截所有请求
• SecondInterceptor:拦截所有请求
• ThreeInterceptor:拦截所有请求

FirstInterceptor

@Component
public class FirstInterceptor implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("FirstInterceptor1---preHandle");
        request.setAttribute("start",System.currentTimeMillis());
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("FirstInterceptor1---postHandle");
        
        Long start= (Long) request.getAttribute("start");
        Long end=System.currentTimeMillis();
        System.out.println("请求执行时间："+(end-start));
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.out.println("FirstInterceptor1---afterCompletion");
    }
}

SecondInterceptor

@Component
public class SecondInterceptor implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("SecondInterceptor2---preHandle");
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("SecondInterceptor2---postHandle");
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.out.println("SecondInterceptor2---afterCompletion");
    }
}

ThreeInterceptor

@Component
public class ThreeInterceptor implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("ThreeInterceptor3---preHandle");
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("ThreeInterceptor3---postHandle");
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.out.println("ThreeInterceptor3---afterCompletion");
    }
}

配置拦截器

@Component
public class WebConfig  implements WebMvcConfigurer {

    @Autowired
    private FirstInterceptor firstInterceptor;
    @Autowired
    private SecondInterceptor secondInterceptor;
    @Autowired
    private ThreeInterceptor  threeInterceptor;


    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(firstInterceptor)
                .addPathPatterns("/**");

        registry.addInterceptor(secondInterceptor)
                .addPathPatterns("/**");

        registry.addInterceptor(threeInterceptor)
                .addPathPatterns("/**");
    }
}

测试拦截器

@RestController
public class HelloController {

    @RequestMapping("/hello")
    public Object hello(){
        return "hello";
    }
}